Arrangement for cutting the threads in a sewing machine when changing the bobbin thread

ABSTRACT

The changing or replenishing of the bobbin thread in a sewing machine in which the sewing is stopped while there is still bobbin thread in the machine, and the over thread is drawn up from the loop-taker mechanism by the thread take-up lever of the machine, with a full bobbin having a length of thread extending therefrom being placed in the machine and the extending thread end is positioned together with the thread end remaining in the machine when making the change.

United States Patent 1191 Giesselmann 1111 3,810,439 14511 May 14, 1974 ARRANGEMENT FOR CUTTING THE- THREADS IN A SEWING MACHINE WHEN CHANGING THE BOBBIN THREAD [76] Inventor: Monica Linne'a Giesselmann,

Oxelgatan 3, 561 00 Huskvarna, Sweden [22] Filed: Dec. 4, 1972 [21] Appl. No.: 311,640

Related U.S. Application Data [62] Division of Ser. No. 44,814, June 9, 1970,

abandoned.

52 us. c1. ..j 112/252 [51] Int. Cl DOSb 65/00 [58] Field of Search 112/122, 130, 180, 186, 112/252, 253, 260, 262

[5 6] References Cited UNITED STATES PATENTS 1,816,308 7/1931 Allen 112/252 2,808,795 10/1957 Wortham 112/186 X 3,038,429 6/1962 Ketterer et a1 112/186 X 3,105,451 lO/l963 Ketterer 112/186 3,118,405 1/1964 Schenkengel 1 1 12/252 3,648,634 3/1972 Van Hazendonk 112/252 FOREIGN PATENTS OR APPLICATIONS 924,304 2/1955 Germany 112/186 Primary Examiner-Werner H. Schroeder Attorney, Agent, or Firm-Holman & Stern 57] ABSTRACT The changing or replenishing of the bobbin thread in a sewing machine in which the sewing is stopped while there is still bobbin thread in the machine, and the over thread is drawn up from the loop-taker mechanism by the thread take-up lever of the machine, with a full bobbin having a length of thread extending therefrom being placed in the machine and the extending thread end ispositioned together with the thread end remaining in the machine when making the change.

3 Claims, 8 Drawing Figures SHEET 2 BF 4 EATEMTEU MAY 14 I974 PATENTEDMAY 14 1914 3.810439 SHHTBUFQ 18 was 3951.

8 Z l 17 O 3 I 23 I r Fig.4

PAIE I MAYM 3 8 0 sum u [If 4 ARRANGEMENT FOR CUTTING THE THREADS IN A SEWING MACHINE WHEN CHANGING THE BOBBIN THREAD This is a division, of U.S. Pat. application Ser. No. 44,8!4, filed June 9, 1970, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a method and an arrangement for changing or renewing the bobbin thread in a sewing machine without removing the workpiece therefrom. The method can be applied to all types of shuttle sewing and is particularly advantageous when stitching accurate seams in, for example, collars, cuffs and when embroidering.

A sudden stop in the supply of bobbin thread will result in a discontinuous seam, which cannot be rectified by subsequent measures.

The normal manner of refilling the bobbin is to stop sewing at some convenient position on the workpiece, then cut the threads, after which the workpiece is removed from the machine and the bobbin is either refilled or replaced with another bobbin. With simple seams, the seam can be simply restarted at the position at which it was stopped and the threads knitted together or fastened to the workpiece.

SUMMARY OF THE INVENTION The present invention provides an alternative method to the aforedescribed known method, in which the workpiece can be left in the machine while the bobbin is being changed or refilled, with the presser foot in a depressed position and the upper'thread passing in an unbroken path through thread guide loops and the eye of the needle. Such a method is advantageous in that the upper surface of the seam remains unbroken and the bobbin thread can be replaced rapidly by simple movements of the hands and with the assistance of auxiliary devices intended for the purpose. The characterizing steps of the method according to the invention are the needle thread is drawn up from the loop-taker mechanism by means of the thread take-up lever of the machine and a full bobbin having a length of thread extended therefrom is placed in the machine and the extended thread end is placed together with the thread end remaining in the machine when making the change. The method is considerably facilitated if the machine is provided with thread guiding and cutting means in the vicinity of the shuttle mechanism. These means are a groove arranged beneath the stitch plate in the bed of the machine and a thread cutting means defined by a knife edge and an abutment movable towards the edge, with the grooves extended from the discharge position to the cutting means.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the inventionwith regard to both the method and the arrangement will now be described with reference to the accompanying drawing, in which FIG. I illustrates the extension of the bobbin thread when inserting a new thread in accordance with the invention, the shuttle mechanism being excluded,

FIG. 2 is a front view illustrating a cutting means positioned in the vicinity of the shuttle mechanism of a sewing machine,

FIG. 3 is a side view of the cutting means in FIG. 2,

- FIG. 4 is a front elevational view illustrating a combined thread holder and cutting means at the side of the shuttle mechanism, seen in front view,

FIG. 5 is a view taken along the line V-V in FIG. 4, the view being on an enlarged scale,

FIG. 6 is a front elevational view illustrating an. arrangement with separate thread braking and cutting means on a shuttle mechanism,

FIG. 7 is a view taken along the line VIIVII in FIG. 6, the view being on an enlarged scale.

FIG. 8 is a perspective view of the embodiment of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION When changing the bobbin, the thread fastening means should be in its top position, so that nothing obstructs the upper or over thread in the thread looping means. Normally, there still remains a length of thread in the bobbin to be changed and one of the threads is thus embedded in a seam being sewn. When the bobbin is removed from a sewing position 1, where overlying thread 2 and bobbin thread 3 pass in different directions, the thread is drawn to a cutting means positioned as shown by numerals 4 and 5 suitably situated at one side of the sewing position. The remaining end 6 of the bobbin thread or under thread then hangs freely from the sewing position and, when the seam'is finished, will be positioned on the under surface of the workpiece. A new bobbin filled with thread is placed in position and an end 7 of the thread is drawn from a thread feeding position 8 on the bobbin and .cut, suitably by the same cutting means previously used. When the sewing machine is restarted, the loop of the upper thread picks up the end 7 of the bobbin thread, which is then drawn up towards the sewing position 1. The only sign which indicates that the bobbin thread has been changed the machine is the presence of the two ends 6, 7 on the inside of the workpiece. These ends can be either knotted together or sewn into the workpiece. The important step in the method for obtaining a continuous seam without a break in the upper or overlying thread is that sewing of the seam should be stopped before the bobbin thread has been fully consumed.

The aforedescribed method assumes that a reserve bobbin filled with the same thread as that being used is readily available. If this is not the case, the empty bobbin must be refilled from an extra reel of thread or from the spool or reel carrying the upper thread. With this latter alternative, the upper or overlying thread must be cut suitably between the eye of the needle and the workpiece, so that the upper thread passes unbroken through the thread tensioning means, thread take-up lever, loops and the eye of the needle. The bobbin is then entered on a winder spindle and refilled with the upper thread and placed in position in the machine. The seam is then picked up at exactly the same position at which it was stopped. As a result of breaking the upper thread, it is necessary to tidy the seam to some extent, for example by attaching the ends of the upper thread to the workpiece. This requires no more work, however, than, for instance, of the seam at the beginning and the end of the same.

FIG. 2 illustrates the sewing position of a free-arm sewing machine having a hinged flap 9, behind which is situated a loop-taker mechanism. The frame around the loop-taker mechanism comprises a cover plate 10, through the center ofwhich projects a spool 11 through an opening 12. The cover plate of the loop-taker mechanism structure has arranged in the upper left hand corner thereof (FIG. 2) a shoulder 13 and thereabove is provided a narrow groove 14 which extends from the edge of the opening 12 out towards the left outer edge surface of the cover plate. A front face 15 of the shoulder is inclined obliquely upwards towards the groove 14 and thereby facilitates insertion of the ends 6, 7 of the bobbin thread into the groove. One cover plate securing screw 16 is also countersunk in the shoulder 13. Secured in a wall 17 of the free-arm immediately behind the outlet of the groove 14 is a knife 18 and on the flap 9 is an abutment 19 which cooperates with the knife in such a manner that the abutment is moved towards the knife 18 as the flap is closed. Those portions of the thread ends 6, 7 which then lie over the knife are automatically cut and the threads 6, 7 remain in the groove. The thread end 7 arriving from the spool in capsule 11 is removed from the knife 18, whereby the upper thread, when the machine is started, grips the lower thread and pulls it up towards the sewing position in'the direction shown by dotted line 20 in FIG. 2. The other end 6 of the bobbin thread is drawn gradually from the groove when the workpiece is moved forwards beneath a presser foot 21.

In embodiment illustrated in the FIGS. 4 and 5, the loop-taker mechanism and the loop-taker cover plate are shown together with a different type of cutting means than that previously described. A spring plate 22 having an outwardly projecting tongue 23 is attached and tensioned against the cover by a screw 24 passing through the same. The tongue has an outwardly swung portion in which is located a V-shaped recess 25 having a sharp edge 26 located at the bottom thereof. When the bobbin is removed for refilling or replacement, the bobbin thread can be cut on the edge 26, as can the superfluous portion of the thread wound on the bobbin when the bobbin is replaced in the machine. The two threads 6', 7' are placed between the tongue and the cover plate, in a fissure 27, after which they are drawn into the recess and pressed against the sharp edge. The thread ends are then held by the pressure of the tongue against the cover plate and are released approximately simultaneously subsequent to a certain degree of movement of the workpiece forwards of the sewing position.

The embodiment illustrated in FIG. 6 is a variation on the embodiment of FIGS. 2 and 3. In FIG. 6, a brake shoe 28 is movably mounted angularly of the groove 14" and is actuated towards the groove by a spring 29 (FIG. 7) in a manner whereby bottom edges 30 of the brake shoe press against the lower side edge of the groove. The brake shoe can be lifted against the action ofthe spring, to enable the threads 6", 7" to be moved into the groove beneath the brake shoe, which then urges the threads against the side edge of the groove, as shown in FIG. 7. As with the embodiment of FIG. 2, the embodiment of FIG. 6 has a knife 18'' mounted adjacent the outlet of the groove 14''. The knife 18 has a V-shaped recess, in which the threads are severed, when they extend from the brake shoe rearwardly through the recess. The threads are released from the brake in the same manner as that described with reference to FIGS. 4 and 5. The advantage afforded by the embodiment of FIG. 6 over the embodiment of FIG. 2 is that none of the ends 6", 7" hang loosely at any time. when the machine is restarted after replenishing the thread, thereby eliminating the danger ofa thread end being visible in the seam, which would be difficult to rectify. This advantage becomes more marked the closer to the sewing position the brake is situated. 1

The means for facilitating changing of the bobbin thread just described are adapted to guide the ends of the bobbin thread and to impart the correct braking effect, so that the newly inserted thread is retained in the brake while more thread is unwound from the bobbin as the upper thread carries the bobbin thread to the sewingposition. On the other hand, the braking action is restricted so as not to present an obstacle to feeding of the workpiece through the machine. Furthermore, adjustment of the length of the thread ends is simplified so that all unnecessary thread is removed subsequent to changing the thread.

The aforedescribed embodiments can be modified without departing from the concept of the invention. Thus, the different members are not restricted to the shown shuttle systems or solely to free-arm machines as illustrated. The positioning of the guide grooves, brake and knife in the described embodiment has been selected in view of the circumstances surrounding the loop-taker mechanism, for example the presence of a loop-taker cover plate. The invention is defined in its entirety in the accompanying claims.

What is claimed is:

I. An arrangement in a sewing machine for assisting in changing or replenishing a bobbin thread in a machine without removing a workpiece therefrom, including a bed enclosing a loop-taker mechanism having a bobbin spool provided with a bobbin thread discharge position, and a plate covering the loop-taker mechanism, the improvement comprising means defining a groove beneath the stitch plate in the machine, and a thread cutting means defined by a knife edge and an abutment movable towards the knife edge with the groove extending from the discharge position to the cutting means.

2. The arrangement as claimed in claim 1, including a brake shoe located in the groove, and the brake shoe being angularly movable towards one side surface of the groove thereby holding by friction, thread ends inserted in the groove.

3. An arrangement in a sewing machine for assisting in changing or replenishing a bobbin thread in a machine without removing a workpiece therefrom, including a bed enclosing a loop-taker mechanism having a bobbin spool provided with a bobbin thread discharge between the spring plate and the bed. 

1. An arrangement in a sewing machine for assisting in changing or replenishing a bobbin thread in a machine without removing a workpiece therefrom, including a bed enclosing a loop-taker mechanism having a bobbin spool provided with a bobbin thread discharge position, and a plate covering the loop-taker mechanism, the improvement comprising means defining a groove beneath the stitch plate in the machine, and a thread cutting means defined by a knife edge and an abutment movable towards the knife edge with the groove extending from the discharge position to the cutting means.
 2. The arrangement as claimed in claim 1, including a brake shoe located in the groove, and the brake shoe being angularly movable towards one side surface of the groove thereby holding by friction, thread ends inserted in the groove.
 3. An arrangement in a sewing machine for assisting in changing or replenishing a bobbin thread in a machine without removing a workpiece therefrom, including a bed enclosing a loop-taker mechanism having a bobbin spool provided with a bobbin thread discharge position, and a stitch plate covering the loop-taker mechanism, the improvement comprising a braking shoe defined by a spring plate resiliently mounted to the machine bed by a screw, and a knife edge, the knife edge being positioned on the spring plate and constituting cutting means for thread ends inserted in a fissure between the spring plate and the bed. 